Method and system of coating polymer solution on a substrate in a solvent saturated chamber

ABSTRACT

A method and apparatus of coating a polymer solution on a substrate such as a semiconductor wafer. The apparatus includes a coating chamber having a rotatable chuck to support a substrate to be coated with a polymer solution. A dispenser to dispense the polymer solution over the substrate extends into the coating chamber. A vapor distributor having a solvent vapor generator communicable with the coating chamber is included to cause a solvent to be transformed into a solvent vapor. A carrier gas is mixed with the solvent vapor to form a carrier-solvent vapor mixture. The carrier-solvent vapor mixture is flown into the coating chamber to saturate the coating chamber. A solvent remover communicable with the coating chamber is included to remove excess solvent that does not get transformed into the solvent vapor to prevent the excess solvent from dropping on the substrate.

BACKGROUND

1. Field

Aspects of this disclosure pertain to a method and system of coating apolymer solution such as a photoresist polymer solution over a surfaceof a substrate such as silicon substrate. The coating occurs in asolvent saturated chamber to prevent evaporation of the polymer solutionduring coating.

2. Discussion of Related Art

The manufacture of integrated circuits involves the transfer ofgeometric shapes on a mask to the surface of a semiconductor wafer.Thereafter the semiconductor wafer corresponding to the geometric shapesor corresponding to the areas between the geometric shapes is etchedaway. The transfer of the shapes from the mask to the semiconductorwafer typically involves a lithographic process. This includes applyinga photosensitive pre-polymer solution to the semiconductor wafer. Thesolvent in the pre-polymer solution is removed by evaporation, and theresulting polymer film is then baked. The film is exposed to radiation,for example ultraviolet light, through a photomask supporting thedesired geometric patterns. The images in the photosensitive materialare then developed by soaking the wafer in a developing solution. Theexposed or unexposed areas are removed in the developing process,depending on the nature of the photosensitive material. Thereafter thewafer is placed in an etching solution which etches away the areas notprotected by the photosensitive material. Due to their resistance to theetching process, the photosensitive materials are also known asphotoresists. These may for instance be sensitive to ultraviolet light,electron beams, x-rays, or ion beams.

The high cost of the photoresist pre-polymer solutions makes itdesirable to devise methods of improving the efficiency of the coatingprocess so as to minimize the amount of the polymer solution required tocoat a substrate. Furthermore, thickness uniformity of the photoresistlayer is an important criterion in the manufacture of integratedcircuits. It ensures satisfactory reproduction of the geometric patternson the semiconductor wafer. The solvent in the photoresist tends toevaporate during application, increasing the viscosity of the polymersolution and inhibiting the leveling of the resulting film. Thisproduces thickness non-uniformities. It is therefore desirable to beable to control the rate of evaporation of solvent from the polymersolution during the coating process.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is illustrated by way of embodiments and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. The invention may best beunderstood by referring to the following description and accompanyingdrawings that are used to illustrate embodiments of the invention. Inthe drawings:

FIG. 1 illustrates an exemplary embodiment of a coating apparatus;

FIG. 2 illustrates a cross-sectional side view of a collector andshowerhead provided within the coating apparatus shown in FIG. 1;

FIG. 3 illustrates a top view of a collector provided within the coatingapparatus shown in FIG. 1;

FIG. 4 illustrates a top view of a showerhead provided within thecoating apparatus shown in FIG. 1;

FIG. 5 illustrates an exemplary method of coating a polymer solution ona surface of a substrate; and

FIG. 6 illustrates another exemplary method of coating a polymersolution on a surface of a substrate;

The features of the described embodiments are specifically set forth inthe appended claims. The embodiments are best understood by referring tothe following description and accompanying drawings, in which similarparts are identified by like reference numerals.

SUMMARY

In one aspect of the invention, an embodiment includes an apparatus ofcoating a polymer solution on a substrate such as a semiconductor wafer.The apparatus includes a coating chamber having a rotatable chuck tosupport a substrate to be coated with a polymer solution. A dispenser todispense the polymer solution over the substrate extends into thecoating chamber. A vapor distributor having a solvent vapor generatorcommunicable with the coating chamber is included to cause a solvent tobe transformed into a solvent vapor. A carrier gas is mixed with thesolvent vapor to form a carrier-solvent vapor mixture. Thecarrier-solvent vapor mixture is flown into the coating chamber tosaturate the coating chamber. A solvent remover communicable with thecoating chamber is included to remove excess solvent that does not gettransformed into the solvent vapor to prevent the excess solvent fromdropping on the substrate.

In another aspect of the invention, an embodiment includes a method ofcoating a polymer solution over a surface of a substrate. The methodincludes securing a substrate to be coated with a polymer solution in acoating chamber having a rotatable chuck that supports the substrate.The method further includes generating a carrier-solvent vapor mixtureand saturating the coating chamber with the carrier-solvent vapormixture, wherein a carrier gas is mixed with the solvent vapor to formthe carrier-solvent vapor mixture. Excess solvent that does not gettransformed into solvent vapor is removed to prevent the excess solventfrom dropping on the substrate. The polymer solution is dispensed over asurface of the substrate while the coating chamber is saturated with thecarrier-solvent vapor mixture. The substrate is rotated to spread thepolymer solution over the surface of the substrate.

DETAILED DESCRIPTION

Exemplary embodiments are described with reference to specificconfigurations and techniques. Those of ordinary skill in the art willappreciate the various changes and modifications to be made whileremaining within the scope of the appended claims. Additionally, wellknown elements are not set forth in detail in order to not obscure thesubstance of the embodiments of the present invention. The followingdescription and drawings are illustrative of the invention and are notto be construed as limiting the invention.

The embodiments of the present invention direct to an apparatus andmethod of coating a surface of a substrate such as a semiconductor waferwith a polymer solution such as a photoresist solution. In particular,the embodiments pertain to spin coating a surface of the substrate withthe polymer solution in a volatile solvent saturated environment. Thesubstrate can be a semiconductor wafer used in the manufacture ofintegrated circuits (e.g., monocrystalline silicon). The substrate canalso include patterns and structures created on the substrate. Thecoating occurs in a coating chamber that is saturated with a solventvapor such that when coating takes place, the evaporation of the polymersolution is minimized. Such a coating environment with volatile solventsaturation prevents polymer solution evaporation thus, improving thethickness uniformity of the polymer to be coated on the substrate. Inaddition, such coating environment reduces the amount of polymersolution needed to do the coating.

The embodiments will be described with more reference to semiconductorwafers used in the manufacture of integrated circuits and theapplication of photoresist solutions to a surface of a semiconductorwafer. It will be appreciated that films or coatings used in integratedcircuit manufacture are not limited to photoresist layers and could, forexample, include materials such as organic planarization films,anti-reflection films, siloxane spin-on-glass films, polyimide films,and polimide siloxane films.

In one embodiment, a polymer solution such as a photoresist solution hasa solute content ranging from about 10% to about 50% by weight. In oneembodiment, the photoresist solution is a deep-ultraviolet photoresistpolymer.

In one aspect, the coating occurs in a coating apparatus that has acoating chamber having a rotatable chuck that can secure and support asubstrate to be coated. A dispenser to dispense a polymer solution overa surface of the substrate is extended into the coating chamber. A vapordistributor (e.g., an atomizer or an ultrasonic device) is configuredand positioned such that it is communicable with the coating chamber.The vapor distributor includes a solvent vapor generator that cantransform a solvent into a solvent vapor. A carrier gas is mixed withthe solvent vapor to form a carrier-solvent vapor mixture. The carriergas functions to carry the solvent vapor into the coating chamber. Thecarrier gas also functions to provide a “spray action” for deliveringthe solvent vapor into the coating chamber. The carrier-solvent vapormixture is flown into the coating chamber via the solvent distributor tosaturate the coating chamber. A solvent remover is configured to becommunicable with the coating chamber to remove excess solvent that doesnot get transformed into the solvent vapor. This prevents excess solvent(or droplets of solvent) from dropping or dripping on the substrate andcausing non-uniformity in the polymer solution and consequently, thenon-uniformity in the polymer layer to be formed. The solvent removercan be an atomizer or an ultrasonic device configured to cause theexcess solvent to be sucked out of the coating chamber. A carrier gassource and a solvent source are coupled to the vapor distributor tosupply the carrier gas and the solvent to the vapor distributor. Apolymer solution source is coupled to the dispenser to supply thepolymer solution to the dispenser.

In some aspects, a fluid sensor is included in the coating chamber todetect the presence of the excess solvent so as to cause the solventremover to activate and remove the excess solvent before the solventdrips down on the substrate.

In some other aspects, the coating chamber includes a collector placedabove a coating area that is adjacent the substrate. The carrier-solventvapor mixture passes to the collector prior to passing into the coatingarea. The collector has a raised edge that prevents excess solvent fromspilling into the coating area. Only the carrier-solvent vapor mixturecan float over the collector and into the coating area. A showerhead maybe placed below the collector and above the coating area to act as asecond screener for the carrier-solvent vapor mixture. The showerheadhas a plurality of openings sized to allow acceptable mist or vapor topass through (e.g., openings ranging from 0.010 μm to 0.085 μm). Thecarrier-solvent vapor mixture passes into the coating area through theopenings. The showerhead also functions to uniformly distribute thecarrier-solvent vapor mixture into the coating area. The descriptionbelow discusses in more details a coating apparatus of the exemplaryembodiments of the present invention.

FIG. 1 illustrates a coating apparatus 100 in accordance with exemplaryembodiments of the present invention. The coating apparatus 100 includesa housing 101 that houses a coating chamber 102. A rotatable supportchuck 104 is mounted in the coating chamber 102. The rotatable supportchuck 104 supports a substrate 106, which in some embodiments, is awafer or a silicon wafer. The substrate 106 may include structures orpatterns formed thereon as is known in the art. The rotatable supportchuck 104 passes through an opening 114 created at the bottom of thecoating chamber 102. The rotatable support chuck 104 is mounted on anaxel 112 which can spin or rotate the rotatable support chuck 104.

The housing 101 includes a substrate transport door 110 to allow for thetransporting the substrate 106 in and out of the coating chamber 102. Arobotic device 108 that includes a substrate handler can be used to movethe substrate 106 in and out of the transport door 110. The transportdoor 110 is shut after the substrate 106 is placed or secured on thechuck 104. The transport door 110 is also shut during the coatingprocess.

A dispenser 116 is extended into the coating chamber 102. The dispenser116 is coupled to a dispensing line 160 that is communicable with apolymer solution source 158. The dispenser 116 dispenses the polymersolution on a surface of the substrate 106 for coating. In oneembodiment, the dispenser 116 rests on the side of the substrate 116 andmoves toward the center of the substrate 116 for coating. The dispenser116 is configured to dispense the polymer solution at a controlled rateover the substrate 106. In one embodiment, a controller 115 is coupledto the polymer solution source 158, the dispensing line 160, and/or thedispenser 116 to control the volume and rate to dispense the polymersolution on the substrate 106. The controller 115 can also be configuredto control the dispenser 116 so that the dispenser 116 can move into andout of the coating position (e.g., center or side of the substrate 116).

A vapor distributor 118 is included in the coating apparatus 100. Thevapor distributor 118 is communicable with the coating chamber 102. Inone embodiment, the vapor distributor 118 is placed on top of thehousing 101 and above the coating chamber 102. The vapor distributor 118vaporizes, transfers, or converts a solvent into a solvent vapor andmixes the solvent vapor with a carrier (e.g., nitrogen (N₂)) gas to forma carrier-solvent vapor mixture. The solvent should be similar orcompatible to the solvent of the polymer solution to be dispensed. Inone embodiment, the solvent is one typically used in a photoresistsolution, typically used in semiconductor processing. The vapordistributor 118 also passes or injects the carrier-solvent vapor mixtureinto the coating chamber to saturate the coating chamber 102 with thecarrier-solvent vapor mixture. Saturating the coating chamber 102 helpscontrolling the atmosphere above the substrate 106 surface and controlthe rate of solvent evaporation from the polymer solution coating. Inone embodiment, the vapor distributor 118 includes a solvent vaporgenerator that functions to transform the solvent into the solventvapor. In one embodiment, the vapor distributor 118 is an atomizer andin another embodiment, the vapor distributor 118 is an ultrasonic devicethat can vaporize the solvent.

In one embodiment, the vapor distributor 118 includes a first conduit138, a second conduit 140, and a third conduit 142. The vapordistributor 118 can be an atomizer that is readily and commerciallyavailable. The first conduit 138 communicates to a solvent source 144,which supplies the solvent to the vapor distributor 118. The solventsource 144 is hooked up to a line 176 that leads into the conduit 138.The solvent source 144 can be a pressurized canister (e.g., atapproximately 10 psi) so that once open, the solvent can be supplied tothe vapor distributor 118. In one embodiment, the solvent source 144 iscoupled to a pressure source 148 (e.g. an inert gas such as N₂ gas)through a line 174. The pressure source 148 can cause the transfer ofthe solvent to the vapor distributor 118 by supplying a sufficient andsmall amount of inert gas to the solvent source 144. In one embodiment,N₂ gas is flown into the solvent source to cause the solvent to betransferred to the vapor distributor 118. Valves 172 and 168 areprovided to allow for the flow of the solvent into the vapor distributor118. A flow controller 170 can also be provided to control the flow rateof the solvent into the vapor distributor 118.

A carrier gas source 146 is coupled to the vapor distributor 118 tosupply the carrier gas into the vapor distributor 118. The carrier gassource 146 is communicable to the vapor distributor 118 through line180, which ends into the second conduit 140 of the vapor distributor118. The carrier gas source 116 includes a valve 178 that once opened,allows for the flow of the carrier gas into the vapor distributor 118. Acontroller 150 may be coupled to the carrier gas source 146 to allow forthe control of the flow of the carrier gas to the vapor distributor 118.In addition, the controller 150 may control other parameter for thecarrier gas flowing from the carrier gas source 146. In one embodiment,the controller 150 controls the temperature of the carrier gas to besupplied to the vapor distributor 118. In one embodiment, the controller150 maintains the carrier gas at a temperature between 18-30° C. as thecarrier gas is being supplied to the vapor distributor 118. A flow meteror a flow control 182 can also be coupled to the carrier gas source 146to allow for the monitoring of the flow rate of the carrier gas.

In one embodiment, the vapor distributor 118 has a height H100 and awidth W100 which make up the space in the vapor distributor 118 wherethe solvent is vaporized and mixed with the carrier gas. The height H100ranges from 4-12 inches and in one embodiment, is about 4.5 inches. Theheight H100 should be sufficient for the solvent to vaporize and mixwith the carrier gas. Too short of a height H100 may cause more excesssolvent to pass into the coating chamber 102 due insufficient mixing andvaporizing space. The width W100 is configured to be sufficient for thedesired angle of the spray of the carrier-solvent vapor mixture. In oneembodiment the carrier-solvent vapor mixture has a spray angle betweenabout 15-35 degrees. The width W100 should be sufficiently wide toaccommodate the spray angle of the carrier-solvent vapor mixture so thatthe mixture can easily be released into the coating chamber 102 withoutobstruction. In one embodiment, the width W100 is about 3.5-6.0 inches.

In one embodiment, a collector 124 is provided within the coatingchamber 102. The collector 124 is placed as closed to the vapordistributor 118 as possible. In one embodiment, the collector 124 isplaced at about 4.5 to 5.5 inches below the vapor distributor 118. Thecollector 124 is positioned within the coating chamber 102 such thatgaps 127 are created between the collector 124 and an inner wall 129 ofthe coating chamber 102. The gaps 127 allow the carrier-solvent vapormixture to flow from the collector 124 into a coating area 194. In oneembodiment, the circumference of the collector 124 is less than an innerarea 129 of the coating chamber by the gaps 127.

The coating area 194 is defined as the area within the coating chamber102 that is adjacent the substrate 106 or the chuck 104. In oneembodiment, only the coating area 194 needs to be saturated with thecarrier-solvent vapor mixtures to prevent evaporation of the solvent inthe polymer solution during coating.

FIG. 3 illustrates the top view of the collector 124. The collector 124can be seen as the first stop for the carrier-solvent vapor mixture.After being ejected from the vapor distributor 118, the carrier-solventvapor mixture meets or passes to the collector 124. In one embodiment,the collector 124 is essentially a round disc having a concentric centerand a plurality of grooves 132 (FIG. 3). Not all of the solvent comingfrom the vapor distributor may have been converted into the solventvapor. There may still be droplets of the solvent 128 that get passedinto the coating chamber 102. Preventing the solvent droplets fromdripping or falling on the substrate 106 is important to control theuniformity of the polymer solution concentration as well as the polymerlayer to be formed on the substrate. The collector 124 functions to stopany excess solvent 128 that is not transformed, vaporized, or convertedinto the solvent vapor from entering a coating area 194 of the coatingchamber 102. The collector 124 does not include openings that the excesssolvent may pass though to enter the coating area 194. The grooves 132in the collector 124 help to direct the excess solvent 128 toward thecenter of the collector 124. The collector 124 also includes a raisededge 126 (FIGS. 1 and 2) to prevent the excess solvent 128 from spillingover the collector 124 and into the coating area 194.

In one embodiment, a showerhead 134 is provided within the coatingchamber 102. The showerhead 134 is placed immediately below thecollector 124. In one embodiment, the showerhead 134 is placed about 0.3to 0.7 inches below the collector 124. The showerhead 134 receives thecarrier-solvent vapor mixture that is passed down from the collector 124through the gaps 127. The showerhead 134 includes a plurality ofopenings 136 (FIGS. 1 and 2) sized to allow the carrier-solvent vapormixture to pass through and saturate the coating area 194 below. In oneembodiment, the openings 136 have sizes ranging from 0.010 μm to 0.085μm. The openings 136 are sized to optimize the flow rate of thecarrier-solvent vapor mixture. The smaller the openings 136, the longerit may take to saturate the coating area. On the other hand, openings136 that are too large may allow unnecessary contamination. In oneembodiment, the openings 136 have sizes ranging from 0.030 μm to 0.080μm. The openings 136 are distributed relatively evenly over theshowerhead to cover a wide area of the coating area.

In one embodiment, a solvent remover 120 is included with the coatingapparatus 100. The solvent remover 120 can be an atomizer or anultrasonic device. The solvent remover 120 is similar to the vapordistributor in that the solvent remover 120 includes a vapor generatorto takes the excess solvent 128 and converts the excess solvent 128 intoa solvent vapor that can be removed from the coating chamber 102 or thecollector 124.

In one embodiment, the solvent remover 120 is coupled to the housing 101as shown in FIG. 1. The housing 101 includes an opening for a solventremoval line 130 to be extended there through. The solvent removal line130 communicates with the solvent remover 120 to transfer the excesssolvent 128 to the solvent remover 120. The solvent remover 120 includesa first conduit 162 where the solvent removal line 130 ends into. In oneembodiment, a carrier gas (e.g., N₂ gas) or a clean dry air 154 is usedto supply into the solvent remover 120 to cause the excess solvent 128to be sucked into the solvent remover 120 and vaporized. The carrier gascan enter the solvent remover 120 from a carrier gas source 154, througha line 167, and a second conduit 164. A valve 169 can also be includedwith the carrier gas source 154 to control the flow of the carrier gasinto the solvent remover 120. The carrier gas or the clean dry air 154is mixed with the excess solvent 128 removed through the solvent removalline 130 and vaporized in the solvent remover 120. The excess solvent128 can then be removed to a container 152 through a third conduit 166of the solvent remover 120. The removed excess solvent can be recycledor removed into the container 162 through a line 165 that extends fromthe third conduit 166 to the container 162.

In one embodiment, a fluid sensor 122 is placed in proximity with thecollector 124. The fluid sensor 122 is configured to detect the solventlevel or the presence of solvent collected at the collector 124. Thefluid sensor 122 can be coupled with a sensor controller 156 which canbe in communication with the solvent remover 120 to cause the removal ofthe excess solvent 128 when the fluid sensor 122 indicates a certainamount of excess solvent 128 is present on the collector 124.

In one embodiment, the coating chamber 102 includes openings 183 and 185to allow for purging of the coating chamber 102. In one embodiment, aninert gas or clean dry air is used to purge the coating chamber 102. Apurge line 187 extends into the opening 185 of the coating chamber 102to allow for an inert gas (e.g., N₂) 184 to be flown into and purge thecoating chamber 102. A valve 186 may also be included to control theflow of the inert gas into the coating chamber 102. In addition, a purgeline 189 extends into the opening 183 of the coating chamber 102 toallow for an inert gas (e.g., N₂) 188 to be flown into and purge thecoating chamber 102. A valve 190 may also be included to control theflow of the inert gas into the coating chamber 102. Each of the purgelines 187 and 189 may be coupled to a flow controller (not shown) tomonitor the flow of the inert gas into the coating chamber 102 for thepurging. Additionally, the coating chamber 102 includes an exhaustoutlet 192 placed proximately at the bottom of the coating chamber 102to allow for the exhausting and cleaning of the coating chamber 102.

FIG. 2 illustrates in details the configuration of the vapor distributor118, the collector 124, the showerhead 134, and the solvent remover 161.In one embodiment, the vapor distributor 118 is an atomizer that canvaporize the solvent that enters the first conduit 138 into a solventvapor. Such an atomizer is known in the art. The vapor distributor 118also mixes the solvent vapor with a carrier gas, such as nitrogen, thatenters the second conduit 140 to create a carrier-solvent vapor mixture.The carrier-solvent vapor mixture is ejected out of the vapordistributor at the third conduit 142 at a particular spray angle (e.g.,15-35 degrees) as illustrated in FIG. 2.

As the carrier-solvent vapor mixture is ejected, some solvent may nothave been vaporized and got ejected from the third conduit 142 as excesssolvent 128. The excess solvent 128 is collected at the collector 124and removed from the collector 124 through the solvent removal line 130as shown in FIG. 2. In one embodiment, the solvent remover 120 is anatomizer. To remove the excess solvent, the carrier gas source 154(e.g., N₂ gas source or clean dry air) is introduced to the solventremover 161, which causes the excess solvent 128 to be moved into thesolvent removal line and into the solvent remover 161. The excesssolvent 128 is vaporized and carried out of the coating chamber with thecarrier gas into the container 152. The excess solvent 128 can also berecycled for coating other substrates. The carrier-solvent vapormixture, in it volatile state, easily floats over the edge 126 of thecollector 124 and passes down to the showerhead 134. The carrier-solventvapor mixture passes through the plurality of openings 136 as shown inFIG. 2 and saturate the coating area 194 that is adjacent the substrate106. After the coating area 194 is saturated with the carrier-solventvapor mixture, the dispenser 116 can dispense the polymer solution(e.g., photoresist solution) over the substrate 106 that is secured tothe support chuck 104.

In one embodiment, an ultrasonic device is included in the vapordistributor 118 to vaporize the solvent. Typically, an ultrasonic devicecan vaporize a liquid into a finer mist than an atomizer or othersimilar devices can. An ultrasonic device can vaporize the solvent intoa solvent vapor having a mist with droplets ranging from 10-20 μm. Usingthe ultrasonic device may eliminate the need for the solvent remover 120to remove the excess solvent since the size of the solvent droplets willbe significantly finer or smaller. Thus, in embodiment, the coatingapparatus 100 includes an ultrasonic device to transform the solventinto the solvent vapor and the coating apparatus 100 does not include asolvent remover 120.

FIG. 5 illustrates an exemplary method 500 of coating a substrate suchas a wafer in a solvent saturated environment. At box 502, a wafer isloaded into the coating chamber such as the coating chamber 102 of thecoating apparatus 100 previously described. The wafer is secured to arotatable support chuck provided within the coating chamber. The wafercan be secured to the support chuck using conventional technique such asvacuum suction.

At box 504, a solvent is vaporized using for example, an atomizer or anultrasonic device. The vaporized solvent is referred to as a solventvapor. In one embodiment, the solvent is a solvent used in a photoresistsolution. The solvent should be of similar composition as the solvent ofthe polymer solution or compatible to the polymer solution that is usedto coat the substrate. In one embodiment, the solvent is vaporized inthe solvent distributor as previously described. In one embodiment, thesolvent is introduced into the solvent distributor at a rate of about0.3 mL/sec to about 3.5 mL/sec for the vaporization. In anotherembodiment, the solvent is introduced into the solvent distributor at arate of about 0.4 mL/sec for the vaporization.

At box 506, the solvent vapor is mixed with a carrier gas to create acarrier-solvent vapor mixture. The carrier gas helps aspirate thesolvent vapor into the coating chamber. The carrier gas is introducedinto the vapor distributor (e.g., the atomizer or the ultrasonic device)where it is mixed with the solvent vapor. In one embodiment, the carriergas is introduced at a rate of about 15-25 L/min (or 250 mL/sec to 420mL/sec). In another embodiment, the carrier gas is introduced at a rateof about 22.5 L/min (or 375 mL/sec).

At box 508, the carrier-solvent vapor mixture is introduced into thecoating chamber to saturate the coating chamber with the carrier-solventvapor mixture. In one embodiment, the carrier-solvent vapor mixture onlysaturates the coating area above the substrate. In one embodiment, thecarrier-solvent vapor mixture is allowed to saturate the coating chamberfor about 5-10 seconds. The duration it takes to saturate the coatingchamber may depend on the volume of the coating chamber or the coatingarea. The duration can also depend on the size of the openings in theshowerhead.

At box 510, with the coating chamber saturated with the carrier-solventvapor mixture, a polymer solution (e.g., photoresist solution) isdispensed over a surface of the wafer. In one embodiment, the polymersolution has a temperature of about 21-25° C. In one embodiment, thepolymer solution is dispensed approximately in the middle of the wafer.The wafer is spun or rotated to spread the polymer solution over thesurface of the wafer. In one embodiment, the wafer is rotated at a speedof about 1000-2000 rmp to spread the polymer solution. The speed of therotation may be varied depending on the desired thickness for thepolymer film to be formed.

As the solvent is vaporized and introduced into the coating chamber someexcess solvent may have been formed or remained. The excess solvent isthe solvent that did not get vaporized. A fluid sensor may be placed inthe coating chamber to detect the presence of the excess solvent so asto initiate the removal process. At box 512, the excess solvent isremoved using a vaporizing process to vaporize the excess solvent (forexample, using an atomizer previously discussed). A carrier gas is usedto help move the excess solvent out of the coating chamber. In oneembodiment, the carrier gas is flown at a rate of about 10 L/min (or 167mL/sec) into an atomizer to cause the excess solvent to be sucked intothe atomizer. In another embodiment, the carrier gas is flown at a rateof about 8 L/min (or 133 mL/sec) to 12 L/min (or 200 mL/sec) into anatomizer to cause the excess solvent to be sucked into the atomizer. Theexcess solvent can be removed after a predetermined number of coatings(e.g., after coating 5-10 wafers), based on a schedule time, or when thesensor indicates the presence of the excess solvent. The excess solventcan be removed at the end of a particular coating or simultaneouslyduring a particular coating. With the excess solvent removed, theuniformity of the concentration of the polymer solution dispensed on thesubstrate as well the thickness of the polymer film to be formed areoptimized. In addition, the concentration of the polymer solution ismore controllable.

FIG. 6 illustrates an exemplary method 600 of coating a substrate suchas a wafer in a solvent saturated environment. At box 602, a wafer isloaded into the coating chamber such as the coating chamber 102 of thecoating apparatus 100 previously described. The wafer is secured to arotatable support chuck provided within the coating chamber. The wafercan be secured to the support chuck using conventional technique such asvacuum suction.

At box 604, a solvent is flown into a first atomizer to atomize orvaporize the solvent into a solvent vapor. In one embodiment, thesolvent is a solvent used in a photoresist solution. The solvent shouldbe of similar composition as the solvent of the polymer solution orcompatible with the polymer solution that is used to coat the substrate.In one embodiment, the solvent is introduced into the atomizer at a rateof about 0.3 mL/sec to about 3.5 mL/sec for the evaporation. In anotherembodiment, the solvent is introduced into the atomizer at a rate ofabout 0.4 mL/sec for the evaporation.

At box 606, the solvent vapor is mixed with a carrier gas to create acarrier-solvent vapor mixture. The carrier gas helps aspirate thesolvent vapor into the coating chamber. At box 608, the carrier-solventvapor mixture is passed to a collector that collects excess solvent notin vapor form and allow the carrier-solvent vapor mixture in vapor formto pass to a shower head and float down to the coating chamber tosaturate the chamber with the carrier-solvent vapor mixture. In oneembodiment, the carrier-solvent vapor mixture is allowed to saturate thecoating chamber for about 5-10 seconds. In one embodiment, thecarrier-solvent vapor mixture only saturates the coating area above thesubstrate. The duration it takes to saturate the coating chamber maydepend on the volume of the coating chamber or the coating area. Theduration can also depend on the size of the openings in the showerhead.

At box 610, with the coating chamber saturated with the carrier-solventvapor mixture, a polymer solution (e.g., photoresist solution) isdispensed over a surface of the wafer. In one embodiment, the polymersolution has a temperature of about 21-25° C. In one embodiment, thepolymer solution is dispensed approximately in the middle of the wafer.The wafer is spun or rotated to spread the polymer solution over thesurface of the wafer. In one embodiment, the wafer is rotated at a speedof about 1000-2000 rmp to spread the polymer solution. The speed of therotation may be varied depending on the desired thickness for thepolymer film to be formed.

The saturation of the carrier-solvent vapor mixture minimizes theevaporation of the polymer solution that is dispensed. Thus, lesspolymer solution is needed to coat the wafer. In addition, thesaturation of the carrier-solvent vapor mixture allows for the wafer tobe spun at a lower speed to achieve a certain thickness in the polymerfilm compared to where the coating environment is not saturated withsolvent vapor.

As the solvent is vaporized and introduced into the coating chamber someexcess solvent may have been formed or remained. The excess solvent isthe solvent that did not get vaporized. A fluid sensor may be placed inthe coating chamber to detect the presence of the excess solvent so asto initiate the removal process. At box 612, the excess solvent isremoved using a vaporizing process using a second atomizer. The secondatomizer vaporizes the excess solvent. A carrier gas is introduced intothe second atomizer to cause the excess solvent to be transferred to thesecond atomizer. In one embodiment, the carrier gas is flown at a rateof about 10 L/min (or 167 mL/sec) into the second atomizer to cause theexcess solvent to be sucked into the atomizer. In another embodiment,the carrier gas is flown at a rate of about 8 L/min (or 133 mL/sec) to12 L/min (or 200 mL/sec) into the atomizer to cause the excess solventto be sucked into the atomizer. The excess solvent can be removed aftera predetermined number of coatings (e.g., after coating 5-10 wafers),based on a schedule time, or when the fluid sensor indicates thepresence of the excess solvent. The excess solvent can be removed at theend of a particular coating or simultaneously during a particularcoating. With the excess solvent removed, the uniformity of theconcentration of the polymer solution dispensed on the substrate as wellthe thickness of the polymer film to be formed are optimized. Inaddition, the concentration of the polymer solution is morecontrollable.

In one embodiment, a controller (e.g., a processor or microprocessoroperated on a computer) (not shown) is included in the coating system 10to control the operation of the components of the system 100. Forexample, the controller may control the flow of the polymer solution,the functions of the pump 102, the dispensing valve 132, the enablevalve 102, and the momentary valve 112. The controller may also controlthe shut down of the valve 104 when the sensor 126 indicates that thelevel in the polymer solution source 108 is insufficient for drawing orchanneling polymer solution. The controller may also control themomentary valve 112, e.g., to keep the momentary valve 112 open for apredetermined amount of time (e.g., 1-7 seconds) to allow a flow ofinert gas into the polymer solution source 108 to transfer the polymersolution into the buffer bank 106. The controller may also control theventing of the buffer tank 106, the temperature of the dispensing line114, the dispensing valve 132, and the like of the coating system 100.The controller may be housed in a computer or similar machine. Thecontroller may also be ran by a set of instructions programmed to carryout the coating and/or operation of the coating system 100.

Having disclosed exemplary embodiments, modifications and variations maybe made to the disclosed embodiments while remaining within the spiritand scope of the invention as defined by the appended claims.

1. An apparatus for coating a surface of a substrate with a polymersolution comprising: a coating chamber having a rotatable chuck, therotatable chuck to support a substrate to be coated with a polymersolution; a dispenser to dispense the polymer solution over a surface ofthe substrate; a vapor distributor communicable with the coatingchamber, the vapor distributor including a solvent vapor generator tocause a solvent to be transformed into a solvent vapor, wherein acarrier gas is mixed within the solvent vapor to form a carrier-solventvapor mixture that is flown into the coating chamber to saturate thecoating chamber via the vapor distributor; and a solvent removercommunicable with the coating chamber to remove excess solvent that doesnot get transformed into the solvent vapor to prevent the excess solventfrom dropping on the substrate.
 2. The apparatus of claim 1 comprising:a fluid sensor placed within the coating chamber to detect the presenceof the excess solvent that do not get transformed into the solventvapor, the fluid sensor capable of causing the solvent remover to removethe excess solvent.
 3. The apparatus of claim 1 comprising: a collectorto collect the excess solvent, the collector placed above a coating areawithin the coating chamber, the collector having a raised edge toprevent the excess solvent from spilling into the coating area; and asolvent removal line placed in communication with the collector toremove the excess solvent.
 4. The apparatus of claim 3 wherein thecollector comprises a plurality of groves.
 5. The apparatus of claim 1comprising: a showerhead having a plurality of openings, the showerheadbeing placed above a coating area within the coating chamber, whereinthe carrier-solvent vapor mixture flows into the coating area throughthe plurality of opening to saturate the coating area.
 6. The apparatusof claim 5, wherein the plurality of openings in the showerhead havesizes ranging from 0.010 μm to 0.085 μm.
 7. The apparatus of claim 1comprising: a collector to collect the excess solvent, the collectorplaced above a coating area within the coating chamber, the collectorhaving a raised edge to prevent the excess solvent from spilling intothe coating area: a solvent removal line placed in communication withthe collector to remove the excess solvent; a showerhead having aplurality of openings, the showerhead being placed above the coatingarea and below the collector, wherein the carrier-solvent vapor mixtureis flown down from the collector through the plurality of openings ofthe showerhead to saturate the coating area.
 8. The apparatus of claim1, wherein the solvent distributor comprises a first conduit to receivethe solvent to be transferred into the solvent vapor, a second conduitto receive the carrier gas to be mixed with the solvent vapor, and athird conduit to eject the carrier-solvent vapor mixture into thecoating chamber.
 9. The apparatus of claim 1 further comprises a solventsource and a carrier gas source coupling to the solvent distributor. 10.The apparatus of claim 1 further comprises a container to store theexcess solvent removed from the coating chamber.
 11. The apparatus ofclaim 1 further comprises a polymer solution source coupling to thedispenser to dispense the polymer solution over the substrate.
 12. Theapparatus of claim 1 further comprises a substrate transport door wherethrough the substrate is transferred in and out of the coating chamber.13. The apparatus of claim 1, wherein the solvent remover comprises afirst conduit to receive the excess solvent to be removed from thecoating chamber, a second conduit to receive a carrier gas to force theexcess solvent out of the coating chamber, and a third conduit to leadthe excess solvent vapor into a container.
 14. The apparatus of claim 1wherein the vapor distributor is one of an atomizer and an ultrasonicdevice.
 15. The apparatus of claim 1 wherein the solvent remover is oneof an atomizer and an ultrasonic device. 16-31. (canceled)
 32. Anapparatus for coating a surface of a substrate with a polymer solutioncomprising: a coating chamber having a rotatable chuck, the rotatablechuck to support a substrate to be coated with a polymer solution; adispenser to dispense the polymer solution over a surface of thesubstrate; and an ultrasonic device communicable with the coatingchamber, the ultrasonic device capable of vaporizing a solvent into asolvent vapor, wherein a carrier gas is mixed with a solvent vapor toform a carrier-solvent vapor mixture that is flown into the coatingchamber to saturate the coating chamber via the ultrasonic device.